Start Venu in the tray without creating Settings

[imnakul]

Summary

• Make ordinary, --startup, and --minimized launches start the overlay and tray without constructing the eframe Settings GUI.
• Create Settings on the main thread only after a tray/notch request or explicit --settings; keep early requests queued and coalesce repeated clicks.
• Fall back to visible Settings if the overlay/tray thread cannot start, and route tray restoration through eframe viewport commands.
• Add a Windows runtime smoke test for quiet startup, explicit Settings, hide, and tray restore.

Verification

• Windows-target cargo check --all-targets against the application and smoke-test sources passes via an external build-script-free manifest.
• cargo fmt --check and git diff --check pass.
• The Windows CI runtime smoke test is enabled in this PR.

The eframe GUI no longer exists during normal tray-only startup, avoiding the first-frame visibility behavior that made a hidden NativeOptions viewport insufficient.